Electronically simulated tape echo system



p 2, 1970 E. B. ANDRE ELECTRONICALLY SIMULATED TAPE ECHO SYSTEM FIG.

4 O a 3 m G A I U F U S O B R 4 R 8 2/ m I VN A EU L R n x 0 I O E 4 V w w & f 1 f r J R O R T LC M RE RT F L .l A A EV El U ch N E N vL L G U R E R V U E D. D P IO R E M 0 M 55 P R A M A ATTORNEY.

United States Patent 3,530,249 ELECTRONICALLY SIMULATED TAPE ECHO SYSTEM Eugene B. Andr, Rahway, N.J., assignor to The Ampeg Co., Inc., Linden, N.J., a corporation of New York Filed Oct. 2, 1967, Ser. No. 672,312 Int. Cl. Gh 1/02 US. Cl. 1791 7 Claims ABSTRACT OF THE DISCLOSURE A simulated tape echo circuit for electronic sound systems in which the desired percussive attack of each sound on repetition is attained by electronically modulating the output signal of a reverberation circuit in an amplifier to periodically interrupt the signal. Desired modulation is obtained by feeding the output of the reverberation circuit through a modulator coupled to an oscillator generating a signal of between 4 and 20 cycles per second. The modulator may be of a variety of electronic or photo-electric types such as a neon tube positioned in light transmitting relationship with respect to a photocell controlling the passage of the signal in response to the oscillation of the neon tube.

BACKGROUND OF THE INVENTION This invention relates to the art of electronic sound amplifiers, and more particularly to an improved amplifier for use in providing desired echo effects.

Contemporary musical tastes have given rise to the desirability of being able to produce relatively loud sounds, coupled with what may be broadly referred to as echo effects simulating the playing of the music in a large ball. To this end a variety of amplifier circuits have been evolved for coupling to the output of sound transducers or pickups coupled to a variety of musical instruments such as guitars, basses, organs and accordions, and/or to microphones for use by vocalists.

Previously evolved amplifiers have provided desired echo effects, referring to such effects as reverb, tremolo, or vibrato. Reverb or reverberation effects are those in which the decay of any signal is delayed. Tremolo" or vibrato effects are those in which the amplitude, frequency or pitch of the signal is periodically varied.

Thus, reverberation effects have been provided by feeding an amplified signal from a signal source such as an electronic guitar, record player, radio, or the like to an electromechanical transducer coupled to act as a driver at one end of a coil spring, at the other end of which is a similar transducer which acts as a pickup. The mechanical vibration of the coil spring between the transducers serves to delay and reflect the input signal to provide desired reverberation effects, as shown, for example, in US. Pat. 3,106,610. This arrangement is relatively inexpensive, and though generally satisfactory in simulating the effect of playing in a large hall, is often found inadequate in producing the effects of a true echo because of the failure to provide a percussive attack for each repetition of the signal as is present in a true echo.

A more desirable, but significantly more expensive technique for providing desired echo is by utilizing a tape recorder having a plurality of spaced play-back heads, in which the signal to be echoed is recorded on the tape, with the tape thereafter moved beneath each of the play-back heads. As the tape moves between each of the play-back heads, the signal recorded on the tape is picked up and played back so that dependent on the number of heads, and the rate of movement of the tape, each signal is repeated over and over again to give the desired echo effect. One of the desirable attributes of the ice tape echo effect resides in the simulated repetition of each sounds percussive attack, but the expense of incorporating a multiheaded tape recorder in an amplifier increases expense and militates against its availability for general consumer distribution. Further problems are engendered in the use of tape echo systems arising from the relatively large bulk and weight of the tape recording equipment which makes any amplifier in connection with which the equipment is used difficult to move from place to place, and the maintenance of the tape recorder is involved and costly.

SUMMARY OF THE INVENTION It is with the above considerations in mind that the instant circuitry has been evolved permitting the attainment of desired tape echo effects in an amplifier by the utilization of relatively simple electronic circuit components at relatively small cost without requiring the bulk, weight, expenditure, or maintenance involved in utilizing multiheaded tape recorders to provide desired echo ects.

It is accordingly among the primary objects of this invention to provide desired tape echo effects in a sound amplifier by the utilization of simple electronic components.

A further object of the invention is to provide simulated tape echo effects without requiring the bulk and weight of the conventionally employed tape recorder.

These and other objects of the invention, which will become hereafter apparent, are achieved by modulating the output of the reverberation circuit of the conventional musical sound amplifier to provide desired percussive attack for each repetition of the echoed signal. Modulation, in accordance with an illustrated embodiment of the instant invention, is obtained by coupling a relatively low frequency oscillator to modulating means including a neon tube which is arranged in light transmitting relationship with respect to current flow control means in the form of a photocell arranged in the output circuit of the reverberation amplifier so as to periodi cally interrupt this signal thus providing desired percussive attack at the commencement of each period in which the signal from the reverberation amplifier is audible.

A feature of the invention resides in the fact that the cost of the components for producing the echo. is relatively small as compared to that of a tape recorder, and there is a negligible increase in weight of the amplifier which is generally desired to be readily portable by the musicians who employ these amplifiers.

BRIEF DESCRIPTION OF THE DRAWING The specific details of a preferred embodiment of the invention, and their mode of functioning, will be particularly pointed out in clear, concise and exact terms in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic block diagram of a so-called amplifier (including desired amplification stages and speakers) made in accordance with the teachings of this invention;

FIG. 2 is a wiring diagram showing the details of a modulator circuit as employed in an amplifier embodying the instant inventive concept;

FIG. 3 is a schematic illustration of the typical guitar signal showing the decay of the signal;

FIG. 4 is a schematic illustration of the guitar signal of FIG. 3 showing its appearance as it is fed through a reverberation system employing coil springs or the like indicating the delayed decay of the signal; and

FIG. 5 is a schematic illustration of the signal output of an echo system made in accordance with the teachings of this invention showing how the signal is made to simulate a percussive attack during each period of audibility during its delayed decay.

3 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the drawings, like numerals in the various figures will be employed to designate like parts.

A typical amplification system 10, as shown schematically in FIG. 1 in which a signal source 12 is coupled to a preamplifier 14 which is in turn electrically coupled to reverberation driver 16, which is electrically connected to reverberation unit 18, which is electrically coupled to reverberation amplifier 20, coupled to modulator 22. Modulator 22 is connected to receive a signal from oscillator 24 as well as from reverberation amplifier 20, and the output of modulator 22 is fed to amplifier 26 from which the signal is fed to speaker 28.

The signal source may take the form of a microphone used as a pickup for a variety of musical instruments such as guitars, bass viols, accordions, pianos, or as a microphone used by a vocalist. The signal source may also be provided by the so-called electronic musical instruments, such as electronic organs, electronic pianos, electronic basses, and the like, or by radios, record players, and recorders. Depending on the output of the signal source, a preamp 14 may or may not be employed. Where the preamp is employed, it is of a conventional type providing one or more preamplification stages to raise the signal to desired level.

The output of the preamplifier 12 is fed to a reverb driver 16 in the form of an amplifier raising the signal to a strength sufiicient to drive a reverberation unit, such for example as shown in US. Pat. 3,106,610. It is understood by those skilled in the art that the reverberation unit may take any one of a wide variety of forms, but in a preferred embodiment of the invention, as here illustrated, the amplified signal from the reverb driver is fed to an electromechanical transducer which may be illustratively formed to comprise an electromagnet to which the output signal of the reverb amplifier is fed so as to vary the intensity of the electromagnet in accordance with the variations of intensity of the output signal. An armature is positioned for attraction by the electromagnet, and this armature is coupled to a coil spring or the like so that the variations in the magnetic field produce a stretching of the coil spring. At the output end of the coil spring, an electromagnetic transducer acting as a pickup is positioned, which transducer is similar to the aforedescribed transducer. This pickup transducer is then coupled to modulator 22, as illustrated in FIG. 2.

The reverberating signal from reverb unit 18 produced as a result of the vibration of the coil spring, is illustratively shown as fed to the grid of triode 30 which may be employed in reverb amplifier 20. The output from the plate of triode 30 is fed via capacitor 31 to the modulator 22.

Modulator 22 comprises a triggering element in the form of neon tube 33 coupled to oscillator 24, and physically arranged in light transmitting relationship with respect to current flow control means in the form of photoelectric cell 3-5. In the illustrated embodiment of the invention, modulation control is provided by means of variable resistor 37 connected in parallel across the photocell 35. Volume control of the signal is provided by means of variable resistor 39 arranged in the circuit to the amplifier 26.

Oscillator 24 may take any one of a wide variety of forms, and may be either of a multivibrator type, a relaxation type, a sinusoidal type or any of a wide variety of oscillators producing a repetitive signal of between 4 and 20 cycles per second, preferably subject to selective control within the desired operating range.

OPERATION In use, the specific details of the circuitry of the preamp 14, reverb driver 16, reverb until 18, and reverb amplifier 20 and 26 may take any one of a wide variety of forms 4 such, for example as shown in the circuit diagram of Model No. GS-12R of the Ampeg Co., Inc., Linden, NJ. The signal source may, as will be understood by those skilled in the art, be provided from a variety of sources such as electronic instruments, microphone pickups, or the like.

Modulation of the reverberating signal from the reverb amplifier 20 to provide desired percussive attack on each repetition of the signal echoed as a result of passage of the signal through the reverb unit is provided in modulator 22. The neon tube 33 is caused to fire at a frequency as determined by the output of the signal from oscillator 24, which as noted above, is selected to provide a frequency of oscillation of between 4 and 20 cycles per second. The on-off flashing of the neon tube 33 triggers photocell 35 to become conducting or nonconducting, depending on the type of photocell selected. As here illustrated, it is contemplated that the photocell will be conducting when the neon tube 33 will be flashing. When the photocell 35 is conducting, the signal from the reverb unit will be passed to the amplifier 26, while the signal will be cut oil? during periods of quiescence of the neon tube. As a result of this on-otf passage of the signal from the reverb amplifier 20, the reverberating signal will be provided with an on-olf effect as a result of which the amplified signal to the speaker 28 will give the elfect of a percussive attack at each instance of commencement of audibility of the signal.

As illustrated in FIG. 3, the conventional musical signal, such, for example as provided by the strumming of a guitar, will have a relatively quick decay. When a signal, as shown in FIG. 3, is fed through a reverb unit, the decay of the signal will be delayed, giving the drawn out effect shown in FIG. 4. In order to provide desired percussive attack for the echoing signal shown in FIG. 4 when the signal is passed through the modulator 22, the signal is periodically interrupted, as shown in FIG. 5, to provide an interspersed series of relatively small amplitude ripples with each return of the signal to its normal decaying intensity producing the effect of a new percussive attack It is this repeated percussive attack which is found so desirable in the use of tape echo systems, and it is this percussive attack which is here simulated in a simple, relatively inexpensive, maintenance free fashion by the use of standard electronic components.

The above disclosure has been given by way of illustration and elucidation, and not by way of limitation, and it is desired to protect all embodiments of the herein disclosed inventive concept within the scope of the appended claims.

What is claimed is:

1. In a sound amplification system in which a signal is amplified and fed to a loudspeaker, means for providing the signal with a simulated tape echo effect, said means comprising: reverberating means coupled to receive the signal before it is fed to the speaker and acting to delay the decay of the signal; and modulating means coupled to receive the delayed signal from said reverberating means, said modulating means including means periodically interrupting the passage of the signal from said reverberating means to provide the desired percussive attack of each sound on repetition.

2. In a sound amplification system, as in claim 1, including oscillating means coupled to said modulating means, said oscillating means generating a signal which is fed to said modulating means to control the action thereof.

3. In a sound amplification system, as in claim 1, in which said modulating means include current flow control means and triggering means for said current flow control means.

4. In a sound amplification system, as in claim 3, in which oscillating means are coupled to said triggering means with the signal output of said oscillating means controlling the operation of said triggering means.

5. In a sound amplification system, as in claim 3, in which said current flow control means comprises a photoelectric element in the circuit between said reverberating means and the speaker; and said triggering means comprise a neon tube arranged in light transmitting relationship with respect to said photoelectric element.

6. In a sound amplification system, as in claim 5, in which an oscillator generating a signal of between 4 and 20 cycles per second is coupled to said neon tube to light same at the frequency of oscillation of the oscillator signal.

7. A method of producing a simulated tape echo effect in a sound amplification system in which a signal is amplified and fed to a loudspeaker, said method comprising the steps of: reverberating the signal to delay the decay thereof; and modulating the reverberated signal to periodically interrupt same in its passage to the loudspeaker.

References Cited KATHLEEN H. CLAFFY, Primary Examiner C. W. JIRAUCH, Assistant Examiner US. Cl. X.R. 3323 

